Getter devices of the ring shaped kind



Oct. 6, 1964 P. DELLA PORTA GETTER DEVICES OF THE RING SHAPED KIND 2Sheets-Sheet 1 Filed June 22, 1961 FIG.6A

STARTING TIME (sec) STARTING TIME (SI-:c.)

Oct. 6, 1964 P. DELLA PORTA GETTER DEVICES OF THE RING SHAPED KIND FiledJune 22, 1961 2 Sheets-Sheet 2 I I I 6 l0 TOTAL TIME (sec) I I I I o s 8TOTAL TIME (sac) United States Patent Ofi 3,151,736 Patented Oct. 6,1964 ice 3,151,736 GEFIER DEVICES OF THE RLNG SHAPED KIND Paolo dellaPoi-ta, Via Gallarate 215, Milan, Itaiy Filed .inne 22, 1961, Ser. No.118,860 3 Claims. (Ci. 2%.4)

This invention relates to getter devices for obtaining and keepingvacuum in electronic tubes and more particularly the invention has forits object an improvement in that kind of getter device which isconsisting of an endless channel, such as for instance, a ring shapedcontainer having an U or 1 section.

There are known several embodiments of such getter containers, whichhave wings for the guide of the getter vapours and a shielding disc forprotection against fal ing getter particles, when the getter device isheated inside a tube and the getter vapours are escaping from thecontainer.

The present invention has for its object the achievement of asubstantial improvement in the use of the above said kind of getterdevice in so far as the problem of the undesirable fusion of the gettercontainer is concerned. Such fusion frequently happens in the practicaluse of the said getter devices.

Other objects and advantages of the present invention will becomeapparent from the following description taken in connection with theaccompanying drawing wherein:

FIGURE 1 is a schematic diagram of an electronic tube embodying a gettercontainer according to the present invention;

FIGURE 2 is a graph showing characteristic curves of a ring shapedgetter device;

FIGURE 3 is a graph showing characteristic curves of a ring shapedgetter device with a heat sink;

FIGURE 4 is a schematic diagram of another embodiment of the gettercontainer;

FIGURE 5 is a schematic diagram of another embodiment of the gettercontainer;

FIGURE 6 is a schematic diagram of another embodiment of the gettercontainer;

FIGURE 6a is a section of a portion of FIGURE 6;

FIGURE 6b is a partial section of a portion of FIG- URE 6;

FIGURE 7 is a schematic diagram of another embodiment of the gettercontainer;

8 is a schematic diagram of another embodiment of the etter container;

FIGURE 9 is a schematic diagram of another embodiment of the gettercontainer.

It is known that in order to obtain the evaporation of the active gettermetal contained in the getter container, this latter is heated by a highfrequency current which is inducted in the getter device inside the tubeT from a bobin or coil C which is arranged outside the tube andcoaxially with the getter device, as is diagrammatically shown in FIG. 1of the annexed drawing. The getter container is heated up to a point atwhich the active getter metal contained therein evaporates; possibly thetotal amount of the active getter metal should be evaporated. Theheating must be stopped, however, before the container metal begins tomelt. The fusion of the container metal would have the consequence of adiffusion of metal particles inside the tube and also the diffusion ofgetter vapours in undesired directions, and deposition of said particlesand vapours on parts of the tube, such as the electrodes, where this isundesired. For these reasons, the melting characteristic of the getterdevice is accurately studied in the technics and is known as the meltingcurve, which is related to the starting time and to the total time ofthe getter device, where the starting time is the time from frombeginning of the heating till the beginning of the evaporation of theactive getter metal, and the total time is the time from beginning ofthe heating till the reaching of evaporation of of the active gettermetal contained in the device.

In the manufacture of the electronic tubes it is desired that both thestarting time and the total time should be very brief, so as to beadapted to the production speed of the tubes. On the other hand, it isalso desired that the melting curve of the getter device he as far aspossible from the efficiency curve of 80% as above specified, in orderto surely avoid the fusion of the container.

The present invention achieves a substantial improvement of the getterdevices of the ring shaped kind under the said aspect of the meltingcurve and it essentially consists in that the ring shaped gettercontainer be made with a wing on the internal part of the containerwall, which wing has the task of a heat sink or thermobrake during theheating of the container. Said wing absorbs a part of the heating energyduring the evaporation of the active getter metal and the heatabsorption by said wing becomes particularly efiicient when the getterevaporation is finishing and when the thermostating action of theevaporating getter metal is finishing. The said wing is made in onepiece with the getter container and, therefore, has metallic continuitywith the container. The wing becomes heated with some delay with respectof the getter container; this delay is due to the fact that the highfrequency current which is used for heating the getter container, isrunning mainly along the outer periphery of the container, while theinner part of the container is heated more by conduction than byinducted current. Therefore, on one hand, the wing does not influence atall the swift reaching of the beginning of the evaporation and on thereaching of the 80% evaporation within the desired brief total time,which is in the order of a few seconds, whilst, on the other hand, itsaction is that of delaying the reaching of the melting point of thecontainer and just this is the object of the present invention.

FIGURES 2 and 3 of the annexed drawings show the characteristic curvesin respect of the starting time and the total time, as above specified,of two ring shaped getter devises; namely FIG. 2 shows the curves of aknown ring shaped getter device, having for instance a diameter of 13mm'., and FIG. 3 shows the curves of the same ring shaped getter devicewhich is, however, executed according to this invention with an internalwing made in one piece with the container wall and acting as a heat sinkor thermobrake.

In said figures, the total time is marked on the abscissa and thestarting time is marked on the ordinate. The characteristic curves arethe following LZ=zero curve, that is to say the beginning of theevaporation of the getter metal; R=efiiciency curve of 80%, that is tosay an amount of 80% of the getter metal contained in the device isevaporated; CF =melting curve, that is to say the getter container metalbegins to melt.

It may be seen from FIG. 2which refers to a known getter device-thatwith a starting time of four seconds, that is to say beginning of theevaporation of the active getter metal four seconds after beginning ofthe heating, the 80% efiiciency curve R is reached within a time c whichis less than a second, and the melting curve CF is reached within a timed and this is about two seconds after reaching the R curve. It isevident that such very brief times within which the R curve and themelting curve CF are reached, give rise to serious difiiculty in thepractical use of the getter device in the tube production, since a veryaccurate registration of the high frequency heating is required underthese circumstances. It must be observed here that the getter devicesare not always located in the same position inside the electronic tubesand this creates further difficulties because an eccentric location and/or orientation of the getter device inside the tube may bring as aconsequence a still more critical melting curve than that shown in FIG.2. Indeed, the

practical use of the getter devices of the kind as here considered, hasshown that fusion of the getter co-ntainer happens frequently.

Considering now the characteristic curves of a getter device accordingto this invention, as shown in FIG. 3, is can be seen that with the samestarting time as in FIG. 2, that is four seconds, the 80% efiiciencycurve R is reached within time c, that is more than a second, and themelting curve CF is reached within a time d which is more than threeseconds. It is evident that the increased total time largely avoids thedanger of reaching said melting curve CF in the practical use of thegetter device.

FIG. 3 shows also that with a starting time of five seconds, the 80%efficiency curve R is reached within the time indicated at a to beslightly less than two seconds and the melting curve CF will never bereached, as indicated by time b, Within a total time of fourteenseconds. With the known getter device, as shown in FIG. 2, with astarting time of five seconds, the 80% efficiency curve R is reachedWithin the time indicated at a to be less than one second and themelting curve CF is reached, as indicated by time b, within about threeseconds after the reaching of the R curve.

Figures 4 to 9 of the annexed drawings show, by way of example, someembodiments of the improved getter device with thermobraking wing,according to this invention, all figures showing a ring shaped getterdevice in a sectional view.

FIG. 4 shows a device with a V-shaped container 1 containing activegetter metal 4. The container is filled up with getter metal for only apart of the height of its walls, so that the upper parts of said wallsare forming directional wings to guide the getter vapours as indicatedby arrows and as is known. According to this invention, the internalpart of said container walls is extending inwardly so as to form a wing1' which has the thermobraking action as above said.

FIG. 5 shows another ring shaped getter device with an U-shaped channel,in which the outer wall is bent, with its upper part, to form an anglewith respect of the container axis, while the inner Wall is extendinginwardly to form the wing 1' according to this invention.

FIG. 6 shows a getter device having an U-shaped channel and an inwardlyextending wing 1, as above; this wing 1' is further utilized for fixingon it a disc 2 in order to obtain a circular getter device with aninternal shielding disc. The disc 2 is advantageously fixed onto thewing 1 in a few points only and the fixing can be made by soldering,grappling or the like (see FIGURES 6a and 612).

FIG. 7 shows the same getter device as in FIG. 6, whereby an internalshielding disc 2 is soldered onto the wing 1 by means of a plurality ofbent tongues 2'.

FIG. 8 shows again the same getter device as in FIG. 6, whereby aninternal shielding disc 2 is fixed onto the wing 1, and whereby thisdisc 2 is made with a tongue 2",

which is bent downwardly so that it can be used as a support of thegetter device inside the tube.

FIG. 9 shows again the same getter device as in FIG. 6, whereby the wing1 is made with a tongue 1" which is bent downwardly so that it can beused as a support of the getter device inside the tube. This tongue 1"can be obtained in one piece with the container 1 and its wing 1' in theproduction of the container.

Referring to FIGURES 6 to 8, it is pointed out, that a circular getterdevice with an internal shielding disc was already known before thisinvention. In the known device, however, the shielding disc is made fromone piece with the container. There is, therefore, metallic continuitybetween the container and the disc. The practical use has shown, thatthere is a very high heat absorption by this disc, when heating thegetter device by means of high frequency inducted current. The get termust be heated to a higher temperature in order to obtain evaporation ofthe active getter metal and as a consequence the fusion of the gettercontainer occurs within a very brief time after the reaching of the Rcurve. Such high heat absorption by the shielding disc is avoided, whenthe disc has not metallic continuity with the container, but when it isfixed onto the container in a few points only. A further improvement isobtained, when the support 2" of the getter device, as such shown inFIG. 8, is fixed on to the disc 2, or is part of said disc, instead ofbeing fixed onto the container. In a device as shown in FIG. 7, thesupport is advantageously fixed on to the disc 2, in a point which isdisplaced with respect of the tongues 2'.

Inasmuch as the present invention is subject to many variations,modifications and changes in structural details it is intended that allmatter contained in the foregoing description and shown on theaccompanying drawing be interpreted as illustrative and not in alimiting sense.

What I claim is:

1. In an annular getter container including an evaporable gettermaterial, said container being adapted to be heated to evaporate saidgetter material by means of high frequency heating currents induced inthe outer periphery thereof, integral heat sink means adjacent the innerperiphery of said container, said heat sink means being substantiallyfree of said heating currents and acting to retard the rate oftemperature rise of said container during evaporation of said gettermaterial.

2. The invention defined in claim 1, wherein said heat sink meanscomprises an annular wing member integral and coextensive with the innerperiphery of said annular getter container.

3. The invention defined in claim 2, wherein said wing member furtherincludes an integral depending tongue means, said tongue means beingadapted to support said getter container within an electronic tube.

References Cited in the file of this patent UNITED STATES PATENTS2,430,995 Roos Nov. 18, 1947 2,647,678 Olson Aug. 4, 1953 FOREIGNPATENTS 736,475 Great Britain Sept. 7, 1955 1,054,183 Germany Apr. 2,1959

1. IN AN ANNULAR GETTER CONTAINER INCLUDING AN EVAPORABLE GETTER MATERIAL, SAID CONTAINER BEING ADAPTED TO BE HEATED TO EVAPORATE SAID GETTER MATERIAL BY MEANS OF HIGH FREQUENCY HEATING CURRENTS INDUCED IN THE OUTER PERIPHERY THEREOF, INTEGRAL HEAT SINK MEANS ADJACENT THE INNER PERIPHERY OF SAID CONTAINER, SAID HEAT SINK MEANS BEING SUBSTANTIALLY FREE OF SAID HEATING CURRENTS AND ACTING TO RETARD THE RATE OF TEMPERATURE RISE OF SAID CONTAINER DURING EVAPORATION OF SAID GETTER MATERIAL. 